1. Field of the Invention
This invention relates to a catalytic process for the reaction of a nitrile with an alcohol and water to give the corresponding carboxylic ester and ammonia. No acid reactants are employed.
2. State of the Art
Catalytic processes that do not use acid reactants are known for the reaction of nitriles, alcohol and water to produce esters. The following are representative of this art: German OLS No. 2,832,760; U.S. Pat. No. 3,466,320; U.S. Pat. No. 3,308,153; U.S. Pat. No. 3,313,844; U.S. Pat. No. 2,913,486; and U.S. Pat. No. 2,921,088. None of these known processes, however, employs a catalyst described herein.
Catalytic processes that do not use acid reactants are known for the reaction of nitriles with water to produce the corresponding carboxamides. The following are representative of this art: Bennett, et al., J. Am. Chem. Soc., 95, 3030 (1973) and ibid. 100, 1750 (1978); Yoshida, et al., J. Am. Chem. Soc., 101, 2027 (1979); U.S. Pat. No. 3,670,021; U.S. Pat. No. 3,980,661; U.S. Pat. No. 3,673,250; U.S. Pat. No. 4,096,149; Villain, et al., Tetrahedron Letters, 21, 2901 (1980); and Wainwright, et al., CA, 92, 136021q. The first cited Bennett, et al. publication and U.S. Pat. No. 3,673,250 describe catalysts employed in the process of this invention. Neither of them, however, suggests use of such catalysts to produce esters rather than amides.
The Bennett publication, in column 2, page 3030, states that no hydrolysis of the amide to the acid was observed. Thus, Bennett does not suggest the instant process wherein reaction with a hydroxyl compound is the key process step, albeit to form an ester not an acid. U.S. Pat. No. 3,673,250 states at column 1, lines 16 and 17, that no by-products or almost no by-products are produced. Thus, the patent does not suggest the instant process which has high selectivity for carboxylic acid esters concerning which the patent is silent.
An important class of esters comprises methyl pentenoates made, by the process of this invention, from the corresponding pentenenitriles. Methyl 3-pentenoate and methyl 4-pentenoate can be converted via methoxycarbonylation by known techniques to dimethyl adipate. Dimethyl adipate is readily hydrolyzed to adipic acid which is used commercially in large volume in the preparation of condensation polymers, especially 66 nylon. Accordingly, an improved method for making methyl pentenoates would be of significant commercial importance.
Further, the pentenenitrile reactants are formed readily by the hydrocyanation of 1,3-butadiene. The nitrogen of the HCN used for hydrocyanating 1,3-butadiene comes from ammonia. For the production of methyl pentenoates from pentenenitriles to be most commercially viable, it is necessary that the by-product be ammonia and that the ammonia be readily available for recycle to produce more HCN. The process of this invention is particularly characterized in that ammonia is the by-product of the reaction to make ester, and furthermore, the ammonia is readily available for recycle to produce HCN.
In addition to methyl 3- and 4-pentenoates, esters of aliphatic monocarboxylic acids and dicarboxylic acids made by the process of this invention are useful as solvents, plasticizers, polymer intermediates, and starting materials for pharmaceuticals, agrichemicals, photographic chemicals, and many other articles of commerce.